I locked myself out of my Windows Vista laptop!?

I have a windows vista laptop and the dc jack ended up going bad on it. So instead of getting it fixed immediately I just used the computers at school. Its been almost 3 months and I finally got around to getting my computer fixed. But I ended up forgetting my password to log in. No I dont have my cd that came with it anymore or any other recovery aoftware/hardware. The stuff on the computer is not important so if I have to wipe the hard drive somehow thats not an issue.